1. Field of the Invention
The present invention relates to a method and system for distributing content via Internet Protocol (IP) multicast technology, and more specifically, to a method and system that includes unidirectional communication via satellite and use of a return channel to request distribution of content.
2. Background of the Prior Art
In the current prior art networks, the bulk of traffic is transmitted in unicast form, which requires a separate copy of data to be sent from a source to each requesting client. However, the prior art unicast technology has various problems and disadvantages. For example, because separate copies must be sent for each requesting client throughout the system, a significant quantity of bandwidth is required and available bandwidth is reduced, thus reducing overall system speed and efficiency.
To overcome some of the problems and disadvantages of the prior art unicast network, a prior art multicast technology has been developed. Multicast technology allows a single copy of data to be sent throughout the network to requesting clients, and increases efficiency with bandwidth-hungry Internet applications such as streaming media. Multicast is considered a point-to-multipoint data distribution technology.
In the prior art, satellites operate in a broadcast mode. For example but not by way of limitation, a signal can be up-linked and down-linked to different receivers located within the satellite's footprint (i.e., area of potential broadcast coverage). With respect to Internet communication, prior art satellites have been used to provide bi-directional links between source and destination nodes. As a result, the satellite must be involved in both the transmission as well as the reception for both sides of the satellite link, and the prior art satellite for Internet communication is considered bidirectional. Accordingly, signal transmission to satellites is relatively costly with respect to reception due to the cost of reception and transmission in both directions.
However, the prior art bidirectional satellite has various problems and disadvantages. For example but not by way of limitation, because transmission is so much more costly from a bandwidth perspective than reception, the efficiency of the satellite is reduced.
As a result, a prior art method of IP multicast over unidirectional satellite link has been developed. In the prior art unidirectional IP multicast method, content is transmitted from a source to multiple destinations in a broadcast mode, including multicast file transfer software and extra storage devices at the destination nodes. Prescribed data is transmitted at a predetermined time from a server (i.e., source) to various different locations over the footprint of satellites in a satellite network. The various different locations receive and store the prescribed data for distribution over the network.
The prior art unidirectional IP multicast system operates based on a unicast routing table and conversion system. Because so much of the Internet is still only configured for unicast communication, multicast communication must be converted. In the prior art, multicast-enabled routers use information stored in the unicast routing tables to convert and distribute IP multicast data. A prior art algorithm known as Reverse Path Forwarding (RPF) is used in conjunction with the unicast routing tables to build multicast trees for data distribution throughout the network. However, in the prior art unidirectional routing system, IP multicast fails to properly operate, because the request is always transmitted on a different interface from the interface that receives multicast traffic, as the destination cannot communicate with the source in a unidirectional IP multicast system that uses satellite transmission. The prior art one-way communication prevents selective IP multicast transmission. Another prior art approach requires a “hard join” where the server is forced to transmit data over a unidirectional link without a request.
However, the prior art IP multicast system with unidirectional broadcasting has additional problems and disadvantages. For example, because the prior art system loads traffic in a broadcast mode, all destinations receive the traffic, regardless of whether the destinations have the IP multicast traffic. Thus, there is a substantial waste of bandwidth because the prior art lacks requesting capability in a unidirectional IP multicast system.
Additionally, the prior art system cannot deliver real-time (i.e., live) data (e.g., streaming), because once the data has been distributed, it is first transmitted to storage devices for redistribution prior to being received by the client. Thus, a time delay exists in the prior art system such that live data cannot be IP multicast via unidirectional satellite.
Further, the prior art system cannot distribute content to a multi-hops network in a single execution-cycle. Instead, the prior art system must use re-distribution from the local storage devices at the destination node to distribute content over a multi-hops terrestrial network. Accordingly, it is another disadvantage of the prior art system that storage of data is required at the destination nodes.